Performance decrements due to "divided attention" arise when a person must perform two tasks simultaneously. Presumably this reflects competition for some limited psychological resource or "capacity". This research directly compares such decrements in visual, auditory and mixed-modality tasks. If there is a single, general capacity limit decrements should be similar in all cases. Alternatively, rather different decrements may arise in different modalities. A recently-developed "dual-task monitoring" methodology is employed. Two sources of information are monitored for the occurence of pre-specified targets. The sources may be both visual, both auditory, or one of each. These three cases are to be directly compared on two criteria. The first concerns the overall extent of divided attention decrements, under conditions in which other factors (e.g., task difficulty) are matched across modalities. The second concerns the pattern of decrements revealed by a more detailed "contingent-event analysis". In such analysis, performance on one task is assessed contingent on simultaneous events in the other. Such analyses have shown similar patterns of results in widely different auditory tasks.